System and method for automatic shutoff of a hydraulic fluid flow in the event of a loss in pressure

ABSTRACT

Embodiments of the invention provide for a system and method for operating a hydraulic tool near high-voltage components. The hydraulic tool may be connected to couplers and receiving hydraulic fluid from a pump and returning the hydraulic fluid to a tank in an open center system or returning the hydraulic fluid to a tank in a closed center system. In the event of a loss in pressure the valves in the system change state stopping the flow of hydraulic fluid to the hydraulic tool without the use of electrical components.

BACKGROUND 1. Field

Embodiments of the invention are broadly directed to shutting off fluidflow of a hydraulic fluid in a hydraulic system. More specifically,embodiments of the invention are related to utilizing a system of valvesfor automatic shutoff of a fluid flow to a hydraulic tool in a hydraulicsystem in the event of a loss in pressure in the system.

2. Related Art

Hydraulic power tools are commonly used in place of electric tools whenworking near high-voltage power sources. Power lines and electricalcomponents that carry electricity to households, business, manufacturingplants, or any other facility that uses electricity need maintenance andreplacement. This is typically done using aerial devices that include aboom and utility platform that lifts workers to the power lines andelectrically charged components that need maintenance. The aerialdevices are typically covered in material that is electricallyinsulting, or dielectric material, such that contact with theelectrically charged components is at least partially insulated.Electrical power is also restricted from use at the top of the aerialdevice. This is to prevent the electricity grounding through theelectric infrastructure of the aerial device.

Workers in a utility platform assembly atop a boom of the aerial devicetypically need to use powered tools. Hydraulically powered tools insteadof electrically powered tools are typically used in this situation. Inthe event of a leak or malfunction of the hydraulic tools typicalsystems, not in proximity to high-voltage electricity, employ electriccutoff valves to stop the flow of hydraulic fluid and shut down theequipment. Again, the electrical valves could create an avenue forelectric flow in the event of a contact between the aerial device andhighly-charged electrical equipment. Further, in the event of a leak,hydraulic fluid could flow from the hydraulic system. The hydraulicfluid may be flammable and could come in contact with high-voltageelectrical equipment resulting in a fire. What is needed is a system forautomatic shutdown of the hydraulic tools and equipment without the useof electrical valves or components. Further, what is needed is ahydraulic system, or hydraulic circuit, that prevents the loss, orrelease, of hydraulic fluid from the hydraulic system in the event of abreach or damage to the system components.

SUMMARY

Embodiments of the invention solve these problems by providing a systemfor automatically shutting down a hydraulic system in the event of aleak, malfunction, or loss in fluid pressure. In particular, in a firstembodiment, the invention includes a system for providing a flow of ahydraulic fluid having a fluid pressure to a hydraulic tool, the systemconfigured to prevent excessive loss of the hydraulic fluid when thefluid pressure decreases in the system, the system comprising a pumpproviding the flow of the hydraulic fluid, a first valve directing theflow through a source coupler to the hydraulic tool when the fluidpressure is above a first pressure threshold, a second valve receivingthe flow from a return coupler and directing the flow to a return whenthe fluid pressure is equal to or greater than the first pressurethreshold, a third valve directing the flow from the pump to the returnwhen the fluid pressure is below a second pressure threshold, whereinthe third valve directs the flow from the pump to the source couplerwhen the fluid pressure is above the second pressure threshold.

A second embodiment is directed to a system for providing a flow of ahydraulic fluid having a fluid pressure to a hydraulic tool, the systemconfigured to prevent excessive loss of the hydraulic fluid when thefluid pressure decreases in the system, the system comprising a firstvalve configured to direct the hydraulic fluid to a return when thefluid pressure is below a first threshold, a second valve configured todirect the hydraulic fluid to a return when the fluid pressure is belowa first threshold, and a third valve configured to direct the hydraulicfluid to the first valve when the fluid pressure is above a secondthreshold, wherein when the fluid pressure is above the second thresholdthe first valve is configured to direct the hydraulic fluid to a sourcecoupler and the second valve is configured to direct the fluid from areturn coupler to the return.

A third embodiment is directed to a system for providing a flow of ahydraulic fluid having a fluid pressure to a hydraulic tool, the systemconfigured to prevent excessive loss of the hydraulic fluid when thefluid pressure decreases in the system, the system comprising a firstvalve configured to direct the hydraulic fluid from a pump to a sourcecoupler when the fluid pressure is above a first threshold, a secondvalve configured to direct the hydraulic fluid to a return when thefluid pressure is above a second threshold, wherein the first thresholdis greater than the second threshold, and a check valve configured todirect the hydraulic fluid from a return coupler to the return when thefluid pressure is above the first threshold, wherein the check valve isconfigured to allow fluid to flow therethrough at a third threshold,wherein the third threshold is greater than the second threshold.

This summary is provided to introduce a selection of concepts in asimplified form that are further described below in the detaileddescription. This summary is not intended to identify key features oressential features of the claimed subject matter, nor is it intended tobe used to limit the scope of the claimed subject matter. Other aspectsand advantages of the invention will be apparent from the followingdetailed description of the embodiments and the accompanying drawingfigures.

BRIEF DESCRIPTION OF DRAWINGS

Embodiments of the invention are described in detail below withreference to the attached drawing figures, wherein:

FIG. 1A depicts an exemplary embodiment of an aerial device and autility pole assembly;

FIG. 1B depicts a perspective view of an embodiment of the utilityplatform assembly of the aerial device of FIG. 1A including hydraulicfittings;

FIG. 2 depicts an exemplary embodiment of hydraulic fittings mounted onthe utility platform of FIG. 1B;

FIG. 3 depicts a first exemplary hydraulic system consistent with someembodiments of the invention;

FIG. 4 depicts a second exemplary hydraulic system consistent with someembodiments of the invention;

FIG. 5 depicts a third exemplary hydraulic system consistent with someembodiments of the invention;

FIG. 6 depicts a first flow chart representing a method consistent withcertain embodiments of the invention; and

FIG. 7 depicts a second flow chart representing a method consistent withcertain embodiments of the invention.

The drawing figures do not limit the invention to the specificembodiments disclosed and described herein. The drawings are notnecessarily to scale, emphasis instead being placed upon clearlyillustrating the principles of the invention.

DETAILED DESCRIPTION

The following detailed description references the accompanying drawingsthat illustrate specific embodiments in which the invention can bepracticed. The embodiments are intended to describe aspects of theinvention in sufficient detail to enable those skilled in the art topractice the invention. Other embodiments can be utilized and changescan be made without departing from the scope of the invention. Thefollowing detailed description is, therefore, not to be taken in alimiting sense. The scope of the invention is defined only by theappended claims, along with the full scope of equivalents to which suchclaims are entitled.

In this description, references to “one embodiment,” “an embodiment,” or“embodiments” mean that the feature or features being referred to areincluded in at least one embodiment of the technology. Separatereferences to “one embodiment,” “an embodiment,” or “embodiments” inthis description do not necessarily refer to the same embodiment and arealso not mutually exclusive unless so stated and/or except as will bereadily apparent to those skilled in the art from the description. Forexample, a feature, structure, act, etc. described in one embodiment mayalso be included in other embodiments, but is not necessarily included.Thus, the technology can include a variety of combinations and/orintegrations of the embodiments described herein.

Broadly, embodiments of the invention include a hydraulic system thatprovides energy to a hydraulic tool such that in the event of a drop inpressure the hydraulic system cuts fluid flow from both the pump sideand the return side of the hydraulic system without the use ofelectrical components. The pressure drop may be a leak in a hose, amalfunction of the tool, or a break or malfunction in couplers attachingthe tool to the hydraulic system.

An aerial device 100, constructed in accordance with various embodimentsof the invention, is shown in FIG. 1A. The aerial device 100 generallycomprises a structural base 102 with a boom assembly 104 rotatablymounted thereto. A utility platform assembly 106 is disposed on the boomassembly 104 to provide the utility platform assembly 106 for theaccomplishment of a task by a utility worker. The aerial device 100 maybe controlled to allow a user access to an electrified source such as autility pole assembly 108 while preventing contact between the aerialdevice 100 and the utility pole assembly 108.

The structural base 102 of the aerial device 100 is a selectivelystabilized platform. In embodiments of the invention, the structuralbase 102 may be a utility truck (as illustrated in FIG. 1), a cranebase, an oilrig, an earth-working machine, or a fixed structure. Thestructural base 102 provides stability and a counterweight to a loadbeing supported by the boom assembly 104. The structural base 102 alsoprovides a hydraulic power system, pneumatic power system, electricalpower system, or other system (not illustrated) that powers the movementof the utility platform assembly 106.

The boom assembly 104 broadly comprises an outer boom section 110 and insome embodiments an inner boom section 112. The boom assembly 104presents a proximal end 114 and a distal end 116. The proximal end 114is rotatably and/or pivotably secured to a boom turret 118 of thestructural base 102. The at least one inner boom section 112 is at leastin part disposed within the outer boom section 110. The at least oneinner boom section 112 telescopes to extend or retract into the outerboom section 110. All boom operations as well as some structural baseoperations may be operated by controls disposed in the utility platformassembly 106 or on the structural base 102.

The utility pole assembly 108 as depicted in FIG. 1A may compriseseveral components. The utility pole assembly 108 may include structuralcomponents such as a vertical pole 120 and a cross-member 122. Asdepicted, electrical components may be mounted on the structuralcomponents. A transformer 124 is mounted to the vertical pole 120.Insulators 126 are mounted on the cross-member 122 supporting threephase power lines 128 including power line 130.

The utility platform assembly 106, as best illustrated in FIG. 1B,provides an elevated surface from which at least one utility worker canperform a task. Embodiments of the utility platform assembly 106comprise four bucket sidewalls 132 and a bucket floor 134 thatcollectively form a cavity 136. The utility platform assembly 106 mayalso present a bucket lip 138 along a top portion of at least one bucketsidewall 132. The utility platform assembly 106 may further comprise astep 140 and/or a door (not illustrated) in at least one of the bucketsidewalls 132 to allow for ingress and egress of the utility worker. Theutility platform assembly 106 may also comprise a handrail (notillustrated).

The four bucket sidewalls 132 and the bucket floor 134 of the utilityplatform assembly 106 form the cavity 136. The four bucket sidewalls 132may be unitary, i.e. formed of a single monolithic structure, or theymay be coupled together. The transition between successive bucketsidewalls 132, and/or between the bucket sidewalls 132 and the bucketfloor 134, may be rounded or arcuate. In some embodiments, the utilityplatform assembly 106 presents a horizontal cross-section that issubstantially rectangular. Thus, two of the opposing bucket sidewalls132 may have a greater width than the other two opposing bucketsidewalls 132. In other embodiments, the utility platform assembly 106presents a horizontal cross-section that is substantially square. Otherembodiments of the utility platform assembly 106 may be other shapesabout the horizontal cross-section, such as an ellipse, a circle, aD-shape, a triangle, a trapezoid, a rhombus, or other quadrilateral. Theshape of the cross-section of the bucket may vary along the height ofthe bucket and the bucket shape may be optimized to perform a givenfunction. The bucket may be designed for one or multiple workers. Theworkers may be separated by a structure for safety or may be containedwithin the same cavity 136, as depicted in FIG. 1B.

In embodiments of the invention, the utility platform assembly 106further comprises a set of upper boom controls 142, as best illustratedin FIG. 1B. The set of upper boom controls 142 are configured to bemanipulated by the operator standing in the utility platform assembly106 so as to move the utility platform assembly 106 and/or the boomassembly 104 to a desired location and configuration. In someembodiments, the set of upper boom controls 142 utilize hydraulic powerthat is supplied in the form of a hydraulic fluid by a set of hydrauliclines (not illustrated) discussed in more detail below.

The set of upper boom controls 142 allows the operator to move the boomassembly 104 from within the utility platform assembly 106. The operatorin the bucket may have a better vantage point to know where and how toposition the boom assembly 104 as opposed to the operator on the groundto better avoid contact with the utility pole assembly 108.Additionally, the set of upper boom controls 142 promotes efficiency byallowing the operator to directly control the movement of the boomassembly 104. In embodiments of the invention, an assistant operator(not illustrated) can access a set of lower boom controls (notillustrated) for the duration of the operator being in the utilityplatform assembly 106. This provides a backup to allow the assistantoperator to remove the operator from a situation should the operatorbecome incapacitated or there be a failure in the set of upper boomcontrols 142. The set of upper boom controls 142 may utilize the same ora different mechanism from the set of lower boom controls.

In some embodiments, the boom assembly 104 and the utility platformassembly 106 comprise a dielectric material coat or other insulativematerial that electrically insulates the components from high-voltagepower sources such as the components of the utility pole assembly 108.The material may coat or cover any of the aerial device 100 componentsand assemblies. Any of the aerial device 100 components or assembliesmay also be made of a dielectric or insulative material including thehydraulic couplers 144.

Hydraulic fittings, or couplers 144, provide an attachment forconnecting hydraulic tools to the hydraulic system of the aerial device.The couplers 144 may be in the utility platform assembly 106 as shown inFIG. 1B or may be provided at the structural base 102 or on anycomponent of the aerial device 100 where the hydraulic system may beaccessed. A hydraulic tool (not shown) may connect to the hydraulicsystem using couplers 144. The hydraulic tool may be connected to thehydraulic system and receive hydraulic fluid through a pump coupler 146and may return the hydraulic fluid to a tank or pump through a returncoupler 148. The hydraulic tool attaches hydraulic lines to the couplers144 and receives hydraulic fluid flowing from the pump coupler 146allowing the tool to operate when the pressure of the hydraulic fluidreaches an operational threshold of the hydraulic tool then returningthe fluid through the return coupler 148. Typically, the minimumthreshold pressure for tool operation is 2,000 pounds per square inch(psi), but in some embodiments, the threshold may be below or above thisrequirement.

Broadly, embodiments of the invention relate to a hydraulic system thatautomatically shuts off fluid flow to portions of the system based on aloss in pressure. Embodiments of the invention prevent loss of fluid bypreventing the fluid from flowing out of the system in the event of aleak or damage. The system may cut off the flow to the couplers 144. Insome embodiments, valves block or reroute fluid at both the pump coupler146 and the return coupler 148. In some embodiments, valves block orreroute fluid before the pump coupler 146 and the return coupler 148.This prevents hydraulic fluid from pumping out of the pump coupler 146and from leaking out of the return coupler 148 in the event thatresidual pressure is built up on the return side after the loss inpressure.

A pressure loss may be caused by activities performed by the workers inthe utility platform assembly 106. For example, a common use of theaerial device 100 is tree pruning. Trees may grow to interact with powerlines. The hydraulic tool may be hydraulic tree trimmers, saws, or anyother tool that may be used to trim tree branches. A tree branch mayfall on a hydraulic hose, the hydraulic tool, or the couplers 144 andcause damage resulting in a leak of the hydraulic fluid. The leak maycause a quick drop in the pressure of the hydraulic system causingvalves in the system to change state blocking the flow of hydraulicfluid from the pump coupler 146 and the return coupler 148.

To avoid any electrical discharge while working in close proximity tohigh-voltage power sources the hydraulic system including the cutoffvalves have no electrical components. The hydraulic system may be opencenter or closed center and in embodiments comprises check valves anddirectional control valves but may comprise any valves such as forexample pressure control, flow control, rotary, direct acting, pilot, orany other type valve that can perform the necessary functions describedherein.

In general, embodiments of the hydraulic system include valves, meters,springs, couplers, fluid lines, pipes, pumps, motors, fluids, and anyother components and items necessary for the operation of thebelow-described embodiments of the invention. The hydraulic system maybe powered by energy generated at the aerial device 100 or may beconnected to an auxiliary power source. The hydraulic system may havemultiple access points allowing hydraulic tools to be operated at anycomponent of the aerial device 100 or on the ground in proximity to theaerial device 100. The hydraulic system may be configured such thatmultiple tools may be connected and operated simultaneously. The aerialdevice 100 may include multiple independent hydraulic systems ormultiple hydraulic systems that may be selectively connected, forexample, through valves and/or couplers.

FIG. 2 depicts an exemplary embodiment of hydraulic couplers 200 formounting a hydraulic tool (not shown). In some embodiments, hydrauliccouplers 200 may be couplers 144 depicted in FIG. 1B. The hydrauliccouplers 200 may be mounted in the utility platform assembly 106 asdepicted. The hydraulic couplers 200 may comprise supply couplers 202for receiving hydraulic fluid from a pump (not shown) and returncouplers 204 for sending the hydraulic fluid back to the pump, in thecase of a closed loop system, or a tank (not shown), in the case of anopen loop system. The hydraulic fluid, and pump, may be controlled usingcontrols 206. The controls 206 may control the flow of the hydraulicfluid for creating pressure in the system. The hydraulic fluid pressurein the system may enable operation of the hydraulic tool. The exposedhydraulic couplers 200 and any exposed lines attached to the hydrauliccouplers 200 and the hydraulic tool may become damaged or leak causingthe loss in pressure to the hydraulic system. Upon a drop in pressure inthe system valves within the system may prevent fluid from exiting thesupply couplers 202 and the return couples 204 thus preventing excessiveloss of hydraulic fluid. The system of valves describing embodiments ofthe invention will now be discussed.

FIG. 3 depicts an embodiment of an open center hydraulic system 300. Theopen center hydraulic system 300 comprises a pressure source (P) 302pressurizing a hydraulic fluid within hydraulic lines 304, a tank (T)306, a selectively attached hydraulic tool 308 including a hydraulicmotor (not shown), three check valves, and one two-position two-waynormally closed spring operated directional control valve, or referredto in this embodiment two-way valve 312. The hydraulic tool 308 may beattached to the hydraulic system using the lead (pump or supply) coupler314 and the return coupler 316. In some embodiments, the hydraulic fluidmay be water based or oil based. The pressure source, or pump 302supplying the pressure, may be any fluid pump capable of supplying thepressure needed as described in embodiments of the invention. Thehydraulic tool 308 may be any mechanical tool or equipment usinghydraulic energy as the power source. The hydraulic tool 308 may be handoperated, automatically controlled, hand-held, or mounted on any portionof the aerial device 100. The hydraulic tool 308 may be operational atthe utility platform assembly 106, on the ground, or on any portion ofthe aerial device 100. The hydraulic tool 308 may be configured toattach to the hydraulic system of the aerial device 100 at any accesspoint on the aerial device 100 giving the system flexibility as to thelocation of operation of the hydraulic tool 308. The open centerhydraulic system 300 may be configured to operate at any location of thehydraulic system of the aerial device 100 where the hydraulic tool 308may be attached.

In certain embodiments, the pump 302 may be located in the aerial device100 or may be separate such that it may be attached to the aerial device100 hydraulic system and provide the pressure needed for operating thehydraulic tool 308 separate the aerial device 100. The pump 302 may belocated at the structural base 102, the utility platform assembly 106,or at any location that may be useful to provide the hydraulic energyrequired to operate the hydraulic tool 308. The pump 302 may include amotor for operating the pump 302 or may be powered by the motor orelectrical system of the aerial device 100. The pump 302 motor may beelectric or powered by gas or diesel fuel and may be located in anycomponent of the aerial device 100.

The hydraulic fluid may flow from the pump 302 through the lines 304 ofthe open center hydraulic system 300. When a fluid pressure in thesystem is below a minimal threshold, the fluid flows from the pump 302through the two-way valve 312 to the return 306, which, in an opencenter system, is the tank. When the hydraulic fluid is of sufficientpressure to activate the two-way valve 312 (i.e. above the firstthreshold or setting), the two-way valve 312 switches, in someembodiments closing, directing the fluid flow to the hydraulic tool 308.For example, the two-way valve 312, as depicted in FIG. 3, only allowsfluid to flow to the return 306 below a pressure threshold. Once apressure threshold is met the fluid is directed to flow through thecheck valve 318. Check valve 318 and check valve 320 may open at acombined pressure equivalent to the pressure required for the two-wayvalve 312 to switch. The pressure threshold for the two-way valve 312 tooperate is, for example, 150 psi. Once the pressure of the fluid actingon the two-way valve 312 is at or above the exemplary 150 psi thetwo-way valve 312 switches and directs the hydraulic fluid to flow alongline 322 to line 324 and to the hydraulic tool 308. The pressure isachieved by providing a resistance in the open center hydraulic systemof the exemplary 150 psi. This is done by combining required pressurefor opening the check valve 318 and the check valve 320. The check valve318 may have an operational pressure threshold or setting of, forexample, 100 psi and the check valve 320 may have an operationalpressure threshold or setting of, for example, 50 psi. The exemplarypressures combined, or summed, are equivalent to the minimum pressurethreshold of 150 psi required to move the two-way valve 312. In theclosed position (at a pressure lower than the exemplary 150 psi) thecheck valve 318 and check valve 320 remain closed preventing fluid fromflowing to the hydraulic tool 308 while the two-way valve 312 directsthe hydraulic fluid from the pump 302 to the return 306.

Continuing with the exemplary embodiment in FIG. 3, when the fluidpressure is above the exemplary pressure of the 150 psi threshold thehydraulic fluid is provided to the hydraulic tool 308. The fluidpressure may then increase to a required pressure threshold or settingfor operation of the hydraulic tool 308. At this point the hydraulictool 308 is operational.

In the event of a leak or malfunction, the open center hydraulic system300 cuts off the flow to the hydraulic tool 308. The pump coupler 314and the return coupler 316 which, in some embodiments, may be pumpcoupler 146 and return coupler 148, connect to the hydraulic lines 324of the hydraulic tool 308 to allow the hydraulic fluid to flow from thepump coupler 314 to the hydraulic tool 308 and return via the returncoupler 316. In the event that damage occurs to the couplers, to thehydraulic tool lines 324, or to the hydraulic tool 308, and pressure maydrop below 150 psi and check valve 318 and check valve 320 close andtwo-way valve 312 switches to direct fluid flow from the pump 302 to thereturn 306 via hydraulic line 326. This prevents the hydraulic fluidfrom exiting the open center hydraulic system 300 via the pump coupler314 and the return coupler 316 or from any point on the hydraulic toollines 324 or from the hydraulic tool 308. Realistically there may be aslight delay to allow for the pressure to drop and the check valves toclose, but the delay should be minimal and the majority of the hydraulicfluid should remain in the system. With the open center hydraulic system300 preventing fluid flow beyond the check valve 318 and the check valve320, any damage to the hydraulic tool lines 324 and hydraulic tool 308may be fixed or replaced.

In some embodiments, a check valve 326 may be placed at the end of thepump coupler 314 on the pump 302 side such that the hydraulic tool 308may be attached. Without the check valve 326 the incompressiblehydraulic fluid would prevent attachment. Similarly, the check valve 320may also provide this function to the return coupler 316 such that thehydraulic tool 308 may be attached.

In some embodiments utilizing the hydraulic system depicted in FIG. 3,the setting of check valve 318 may be slightly higher than check valve320 and may be slightly higher than the minimum circulation pressure ofthe hydraulic fluid flowing from the pump 302 to the return 306. Theshift pressure or minimum operational threshold of check valve 320 maybe as high as possible while still allowing connection of the hydraulictool 308 at the return coupler 316 and the shift pressure of thedirection control valve 312 may be greater than the required pressure toopen check valve 318. This configuration allows operation as describedabove.

The minimum pressures required for opening and switching the valves maychange if connect-under-pressure couplers are used. Whenconnect-under-pressure couplers are used, the minimum pressurerequirements may be increased based on the lowest allowable pressure toremain operative at the lowest pressure allowable by the hydraulic tool.However, the pressure relationships between valves may remain the samesuch that the valves shift in the same sequence as described above.

In general, in some embodiments, the couplers are quick disconnectParker FF-371 and FF-372 couplers. Settings of the check valves 326 and320 could be different values than described above without loss ofeffectiveness of the circuit. Settings of the check valves 326 and 320could be changed with connect under pressure couplers. For example, thesetting of check valve 326 may be just low enough to allow forconnection of the coupler 314 and in some embodiments less than 50 psi.The setting of the check valve 318 may be greater than check valve 320and just greater than the circulation pressure. The setting of the checkvalve 320 may be as high as possible while still allowing connection ofthe coupler 316. The shift pressure of the direction control valve 312may be just higher than the pressure required to shift, or open, checkvalve 318.

FIG. 4 depicts a closed center hydraulic system 400 for providinghydraulic energy to the hydraulic tool 402 consistent with someembodiments of the invention. The closed center hydraulic system 400provides fluid from the pump 404 and returns the operational fluid tothe system via the return 406 to the tank. The closed center hydraulicsystem 400 includes at least three spring operated directional controlvalves. Of the three directional control valves one is a two-positionthree-way valve (three-way valve 408) and two are two-position two-wayvalves (pump two-way valve 410 and return two-way valve 412).

The three-way valve 408 is normally open and switches between positionsat a pressure threshold, in this exemplary embodiment 1,800 psi, toprovide fluid to the two two-way valves. When an exemplary pressure of1,800 psi is provided to the three-way valve 408 the valve changesstate, or switches position, directing the fluid to line 416 and totwo-way valve 410 and two-way valve 412. In the exemplary embodimentpresented herein two-way valve 410 and two-way valve 412 are normallyclosed and configured to open at 1,800 psi. Upon opening, the hydraulicenergy is supplied to the hydraulic tool 402, including the hydraulicmotor (not shown), though the pump coupler 420 then via the hydraulictool lines 422. After providing operational energy to the hydraulic tool402, the fluid continues along the hydraulic tool line 424 through thereturn coupler 426 and two-way valve 412 along line 428 and to thereturn 406.

Though in embodiments, the threshold pressure for the three valves is1,800 psi this is exemplary based on a 2,000 psi threshold for thehydraulic tool 402 operation. The pressure threshold for any valve andany hydraulic tool operation may be anything that allows operation ofthe hydraulic tool 402. For example, the three-way valve 408 may have adifferent threshold such that the three-way valve 408 opens at a lowerpressure than the pump two-way valve 410 and the return two-way valve412. The three-way valve 408 may open at an exemplary pressure of 1,500psi and the pump two-way valve 410 and the return two-way valve 412 mayopen at an exemplary pressure of 1,900 psi. This would ensure thatthree-way valve 408 is fully shifted before pump two-way valve 410 andtank two-way valve 412 open.

Continuing with the embodiment depicted in FIG. 4, in the event that thepressure drops below the threshold values of the two-way valves the pumptwo-way valve 410 and the return two-way valve 412 close and the fluidstops flowing to the pump coupler 420 and the return coupler 426. Thisprevents the fluid from flowing out of the system through a leak in theline 424, the hydraulic tool 402, the pump coupler 420, or the returncoupler 426. In the event that the pressure drops below the threshold ofoperation of the three-way valve 408 the three-way valve 408 reverts tothe original, normal state, stopping fluid from the pump 404 at thethree-way valve 408. This prevents large amounts of fluid loss andpossible damage to the hydraulic tool 402 and other equipment. This alsoprevents other problems such as contamination from the hydraulic fluidor fire as described above.

FIG. 5 depicts a closed center hydraulic system consistent with someembodiments of the invention. The closed center hydraulic system 500includes a pump 502, a first directional control valve 504, a seconddirectional control valve 506, a check valve 508, a supply coupler 510and a return coupler 512, for providing hydraulic fluid to a hydraulictool 514. In some embodiments, the pressure to open the check valve 508is approximately 50 psi. This pressure may be any pressure low enough toallow the hydraulic tool 514 to be attached at return coupler 512. Thepressure required to shift the second directional control valve 506 maybe less than the pressure required to open check valve 508. In someembodiments, the pressure required to shift the first direction controlvalve 504 may be 160 psi. This pressure requirement may be differentwhile the other pressure thresholds required to change the valves arechanged to maintain the pressure relationships between valves and tomaintain operation of the hydraulic tool.

Continuing with the embodiment depicted in FIG. 5, when the hydraulicpressure is below a first threshold the hydraulic fluid flows from thepump 502 to the return 516. When the pressure exceeds the firstthreshold the second directional control valve 506 opens allowinghydraulic fluid to flow along line 520, however since no fluid isflowing through the hydraulic tool 514 the hydraulic fluid continues toflow from the pump 502 to the return 516 along line 520. When thehydraulic pressure reaches a second threshold the first directionalcontrol valve 504 opens and the hydraulic fluid flows through the firstdirectional control valve 504 through the hydraulic tool 514 and to thereturn 516 via the check valve 508. Additionally, line 518 becomespressurized closing directional control valve 506 stopping fluid flowfrom line 520 to return 516. In the event of a loss of pressure in thesystem, the first direction control valve 504 switches, the check valve508 closes, the second direction control valve 506 switches, and thehydraulic fluid flows from the pump 502 through the first directioncontrol valve 504 then through the second direction control valve 506and back to the return 516.

The minimum pressures required for opening and switching the valves maychange if connect-under-pressure couplers are used. Whenconnect-under-pressure couplers are used, the minimum pressurerequirements may be increased based on the lowest allowable pressure toremain operative at the lowest pressure allowable by the hydraulic tool.However, the pressure relationships between valves may remain the samesuch that the valves shift in the same sequence as described above.

Turning now to FIG. 6 depicting an exemplary method 600 consistent withembodiments of the invention, at step 602 pressure is supplied from thepump to the system. The pump is made operable by a power source eitherat the pump or connected from an aerial device or independent powersource. The pump acts on the hydraulic fluid to provide pressure to thesystem. The system is an open center system returning the fluid from thevalve system to the tank before returning to the pump.

At step 604, the pressure in the system reaches a first minimum pressurethreshold required to operate at least one valve. In the embodiment ofthe open center system provided above, three operational valves are usedas reference valves. As the pressure is increased in the system thetotal resistance in the system is equivalent to the pressure. When thefirst minimum pressure threshold is reached the at least one valvechanges state, or shifts, directing fluid flow toward the tool. In theopen center embodiment discussed in FIG. 3 the valves consist of onedirectional control valve and at least two check valves. However, thevalves may be any combination that achieves the intended function of thehydraulic circuit.

At step 606, the fluid flows from the pump through the valves throughthe hydraulic tool and to the return. The hydraulic tool is connected toa pump coupler and a return coupler that are positioned on the tool-sideof the hydraulic system such that when the valves are closed the fluiddoes not exit the closed system. The pressure in the system is increaseduntil the pressure reaches a second minimum threshold. The secondminimum threshold is the pressure required for operation of thehydraulic tool.

At step 608, a malfunction causes the pressure drop in the system. Thepressure in the system may drop as a result of damage or a leak in ahose on the hydraulic tool side of the couplers, at a coupler, or at thehydraulic tool. The damage may be the result of faulty equipment, a treebranch falling on the equipment, or misuse by the utility workers.

At step 610, the valves close and stop the flow of fluid from the pumpside and prevent the flow of fluid from the return side. When thepressure drops below the first minimum threshold, the valves may close.The valves, positioned before the couplers may close preventing fluidfrom flowing out of the system through the leak that is located on thehydraulic tool side of the couplers. Stopping the flow at this pointprevents loss of fluid and potential hazards such as slipping,contamination, and fire.

At step 612, the fluid may be directed from the pump to the tank. Avalve, in embodiments described above, a directional control valve,directs the fluid from the pump to the return and, in an open centersystem, to the tank.

Turning now to FIG. 7 depicting an exemplary method 700 consistent withembodiments of the invention, at step 702 pressure is supplied from thepump to the system. The pump is made operable by a power source eitherat the pump or connected from an aerial device or independent powersource. The pump acts on the hydraulic fluid to provide pressure to thesystem. The system is a closed center system returning the fluid fromthe valve system to the pump, bypassing the tank.

At step 704, the pressure in the system reaches a first minimum pressurethreshold required to operate a first valve. In some embodiments, thefirst valve is a two-position three-way valve. When the valve isoperated, the valve directs the fluid to at least a second valve. Insome embodiments, the fluid may also be directed to a third valve.

At step 706, the pressure increases to a second minimum thresholdrequired to operate the second valve and the third valve. In someembodiments, the second valve is a two-position two-way valve and Athird valve may also be present and is a two-position two-way valve. Insome embodiments, the pressure threshold for activating the second valveand the pressure threshold for activating the third valve are differentand a third pressure threshold is needed. When the second valve and thethird valve are activated, the fluid pressure is applied to thehydraulic tool.

At step 708, the pressure is increased to a third threshold that is therequired pressure for operation of the hydraulic tool. In someembodiments, when the pressure threshold for the second valve and thepressure threshold for the third valve are different, a fourth pressurethreshold may be needed for hydraulic tool operation. In someembodiments, the pressure threshold for hydraulic tool operation may beequivalent to the second pressure threshold or the third pressurethreshold.

At step 710, the fluid pressure in the system drops. The pressurereduction may be due to a system malfunction, tool malfunction, or aleak. In some embodiments, when the pressure drops below the thirdthreshold the second valve and the third valve close locking off thetool from the fluid flow. When the fluid pressure drops below the firstthreshold the first valve switches further blocking the fluid flow fromthe system by directing the flow to the return. This may isolate theleak and reduce the amount of fluid loss and damage to the system orother tools and equipment. In some embodiments, the first threshold maybe equivalent to the second threshold such that the fluid flow isdirected to the return through the first valve simultaneously when thesecond and third valve are closed.

At step 712, the valves close and stop the flow of fluid from the pumpside and prevent the flow of fluid from the return side. In someembodiments, when the pressure drops below the second minimum threshold,the valves close. The valves, positioned before the couplers closepreventing fluid from flowing out of the system through the leak that islocated on the hydraulic tool side of the couplers. Stopping the flow atthis point prevents loss of fluid and potential hazards such asslipping, contamination, and fire.

At step 714, the fluid is directed from the pump to the tank. A valve,in embodiments described above, a directional control valve, upon thepressure dropping to the first threshold, directs the fluid from thepump to the return and, in an open center system, to the tank. In aclosed center system, the fluid is directed back to the pump. In someembodiments, the first pressure threshold may be the same as the secondpressure threshold.

The hydraulic components and methods of use provided herein may be usedindividually or in any combination. The components and methods may alsobe used with other components and methods. These methods may provide ahydraulic system, or circuit, that prevents the flow of fluid fromwithin the system to the exterior through a leak by closing valves. Thisoperation may prevent loss of hydraulic fluid and prevent accidents suchas slipping, contamination, or fire.

It should be appreciated that, while the above disclosure has beengenerally directed to the field of aerial devices, embodiments of theinvention may be directed to other fields and uses. For example,embodiments of the invention may be used in stationary cranes, antennas,digger derricks, wood chippers, and other equipment that may utilizehydraulic systems and hydraulic tools and come into contact or used inclose proximity to high-voltage electrically charged components.

Although the invention has been described with reference to theembodiments illustrated in the attached drawing figures, it is notedthat equivalents may be employed and substitutions made herein withoutdeparting from the scope of the invention as recited in the claims.

Having thus described various embodiments of the invention, what isclaimed as new and desired to be protected by Letters Patent includesthe following:
 1. A system for providing a flow of a hydraulic fluidhaving a fluid pressure to a hydraulic tool, the system configured toprevent excessive loss of the hydraulic fluid when the fluid pressuredecreases in the system, the system comprising: a first valve directingthe flow through a source coupler to the hydraulic tool when the fluidpressure is above a first pressure threshold; a second valve receivingthe flow from a return coupler and directing the flow to a return whenthe fluid pressure is equal to or greater than the first pressurethreshold; and a third valve directing the flow from a pump to thereturn when the fluid pressure is below a second pressure threshold;wherein the third valve directs the flow from the pump to the firstvalve when the fluid pressure is above the second pressure threshold,wherein the third valve is disposed between the first valve and thesecond valve.
 2. The system of claim 1, wherein the system is an opencenter hydraulic system and the return flows to a tank.
 3. The system ofclaim 2, wherein the first valve and the second valve are check valvesand the third valve is a two-position two-way normally closeddirectional control.
 4. The system of claim 3, wherein the secondpressure threshold is greater than the first pressure threshold.
 5. Thesystem of claim 4, wherein the second valve is open at a third pressurethreshold that is less than the first pressure threshold.
 6. The systemof claim 1, wherein the system is a closed center hydraulic system andthe return flows to a tank.
 7. The system of claim 6, wherein the firstvalve and the second valve are two-position two-way directional controlvalves and the third valve is a two-position three-way directionalcontrol valve.
 8. The system of claim 7, wherein the third valve isconfigured to direct the hydraulic fluid to flow from a pump to thefirst valve when the fluid pressure is greater than the second pressurethreshold.
 9. The system of claim 8, wherein the third valve isconfigured to direct the hydraulic fluid from the first valve and thesecond valve to the return when the fluid pressure drops below thesecond threshold.
 10. A system for providing a flow of a hydraulic fluidhaving a fluid pressure to a hydraulic tool, the system configured toprevent excessive loss of the hydraulic fluid when the fluid pressuredecreases in the system, the system comprising: a first valve configuredto direct the hydraulic fluid to a return when the fluid pressure isbelow a first threshold; a second valve configured to direct thehydraulic fluid to a return when the fluid pressure is below a firstthreshold; and a third valve configured to direct the hydraulic fluid tothe first valve when the fluid pressure is above a second threshold,wherein when the fluid pressure is above the second threshold the firstvalve is configured to direct the hydraulic fluid to a source couplerand the second valve is configured to direct the fluid from a returncoupler to the return, wherein the first valve is disposed between thesecond valve and the third valve.
 11. The system of claim 10, whereinthe first valve and the second valve are closed when the pressure isbelow the first threshold, and wherein the system is a closed centerhydraulic system and the return comprises a tank.
 12. The system ofclaim 10, wherein the second threshold is at least 1,800 pounds persquare inch.
 13. The system of claim 10, wherein the third valve is atwo-position three-way valve.
 14. The system of claim 10, wherein thefirst valve is a two-position two-way directional control valve.
 15. Thesystem of claim 10, wherein upon the fluid pressure dropping below thefirst threshold the first valve stops the hydraulic fluid from flowingto the hydraulic tool and the third valve directs the hydraulic fluidfrom the first valve and the second valve.
 16. A system for providing aflow of a hydraulic fluid having a fluid pressure to a hydraulic tool,the system configured to prevent excessive loss of the hydraulic fluidwhen the fluid pressure decreases in the system, the system comprising:a first valve configured to direct the hydraulic fluid from a pump to asource coupler when the fluid pressure is above a first threshold; asecond valve configured to direct the hydraulic fluid to a return whenthe fluid pressure is above a second threshold, wherein the firstthreshold is greater than the second threshold; and a check valveconfigured to direct the hydraulic fluid from a return coupler to thereturn when the fluid pressure is above the first threshold, wherein thecheck valve is configured to allow fluid to flow therethrough at a thirdthreshold, wherein the third threshold is greater than the secondthreshold, wherein the hydraulic fluid travels from the pump to thereturn by way of only the second valve or the source coupler and thereturn coupler.
 17. The system of claim 16, wherein the system is aclosed center hydraulic system and the return comprises a tank.
 18. Thesystem of claim 16, wherein the third threshold is equal to or less than50 pounds per square inch.
 19. The system of claim 16, wherein when thefluid pressure drops below the first threshold the first valve preventsthe hydraulic fluid from flowing to the source coupler, and wherein whenthe fluid pressure drops below the second threshold the second valvedirects the fluid flow from the pump to the return.
 20. The system ofclaim 16, wherein the first threshold is equal to or less than 160pounds per square inch.